Londoners enjoying the magnificent sight of sun setting perfectly in the middle of London Eye as seen from Greenwich Park in London, England on the warmest day of the year on April 19, 2018. (Photo by London Viewpoints/Rex Features/Shutterstock)

People dancing to buskers performances in Sai Yeung Choi Street South in Mongkok district, Hong Kong, China, 28 July 2018. After 18 years of unregulated street performances, the street performers were forced to give up the space to vehicular traffic again. (Photo by Jerome Favre/EPA/EFE)

Against the scorching sun, a hungry jackal chases a flock of birds looking for a quick morning snack. Taken in South Africa's Kgalagadi Transfrontier National Park, these images capture the moment a lone hunter tries, and then succeeds, in his pursuit. (Photo by John Mullineux/Solent News)

Everyone wants to get something for nothing - whether it's a lucky upgrade that means you can turn left when you get on a plane instead or heading off into the economy seats, or even getting a few extra features thrown in for free when you buy a new car.

As some of the sharpest businesses around, no-one understands this quite as well as casinos and that's why they all have a system that they call comps. It's short for "complimentary offers" and these are special treats specially designed to reward you for your loyalty to the casino in question. They're basically bonuses.

Trees grow through the windshield of a 1937 Chrysler Imperial as it sits at Old Car City, the world's largest known classic car junkyard Thursday, July 16, 2015, in White, Ga. Over 4,000 classic cars decorate 32 acres of forest which have been turned into a junkyard museum by owner Walter Dean Lewis. The two grew up playing in the cars on the lot which started as a general store selling auto parts in 1931 by Lewis' parents. Lewis stopped selling parts about six years ago when he realized he could sustain the business more as a museum, charging $15 for visitors just looking, and $25 for photographers. Many of the cars have never moved in over 30 years and in some cases, trees now grow through them, even lifting some off the ground. (Photo by David Goldman/AP Photo)

Paris Jackson arrives at the Calvin Klein Collection fashion show during New York Fashion Week at New York Stock Exchange on February 13, 2018. (Photo by Ouzounova/Splash News and Pictures)

Marieke van der Meer from the Netherlands works on her sculpture “Flora” at the sand sculpture show in Binz on Ruegen island, Germany, 09 March 2016. With the motto “Fascination Nature”, 50 sand artists have created oversized sculptures. The sculptors use 16,000 tons of special sand that is pressed into big blocks first and then formed. The 7th sand sculpture show on 5,600 square meters of exhibition ground opens on 12 March 2016. (Photo by Ens Buettner/EPA)

A kid wearing rollerblades hitches a ride via motorbike, in Port-au-Prince, Haiti, Sunday, October 25, 2015. The country held the first-round presidential vote Sunday. Haitians chose between 54 presidential hopefuls and a slew of legislative and municipal candidates. (Photo by Ricardo Arduengo/AP Photo)